1. Field of the Invention
The present invention relates to improvements in a downhole gas separator and, more particularly, to a downhole gas separator adapted to be secured to the lower end of a downhole rod pump in a producing oil well bore, or the like.
2. Description of the Prior Art
When an oil well is initially completed, the downhole pressure may be sufficient to force the well fluid upwardly through the well tubing string to the surface of the well bore. In some instances, however, this downhole pressure is dissipated, and some form of artificial lift is required to elevate the well fluid in the well bore. The most common form of artificial lift in present day use is a downhole rod pump, which is suspended within the tubing string and operably connected to a reciprocating surface unit by a string of sucker rods. In wells which produce gas along with oil, there is a tendency for the gas to flow upwardly into the pump, which may result in a "gas lock" in the pump whereby no fluid is pumped or elevated in the well bore even though the surface unit is continuing to reciprocate. Also, gas in the pump decreases the volume of oil transported to the surface, which decreases the overall efficiency of the pumping unit and reduces oil production.
In order to prevent this entrained gas from interfering with the pumping of the oil, various downhole gas separators have been developed to remove the gas from the well fluid prior to the introduction of the fluid into the pump. A typical present day gas separator comprises a perforated closed end tubing, which is attached to the lower portion of the tubing string disposed within the well casing. The gas separator is perforated in the proximity of the lowermost portion thereof and below the level of the usual perforations of the well casing. As the well fluid flows inwardly through the perforations in the casing, the gas, being lighter than the remaining components of the fluid, tends to travel upwardly in the annulus between the tubing and the casing while the remaining fluid travels downwardly through the perforations in the gas separator and then upwardly through the well tubing to the rod pump. These gas separators have two main disadvantages. First, the gas separators usually remove only a portion of the entrained gas within the well fluid and a substantial portion of the gas is carried downwardly with the well fluid and up into the tubing and the pump. Secondly, these gas separators are normally attached to the well tubing string. During a well work over operation the following steps are involved in removing and replacing the gas separator installed on the tubing string: set up the work rig, pull the pump and rods, take the tubing out of tension, release the tubing anchor, nipple down the tree, pull the tubing, remove the anchor, remove the gas separator, install a new gas separator, install a new or reconditioned anchor, run the tubing, set the tubing anchor, pull tension on the anchor, nipple up the tree, run the rods and the replacement pump, and take down the work over rig. This whole operation normally takes twenty-four hours or more, which is not only extremely expensive, but also greatly increases the possibility of damage to the well structure. The disadvantages of these present day gas separators will be readily apparent.